This invention relates to an ignition system for a multi-valve engine and more particularly to an improved compact ignition system.
To improve the performance of an ignition system for an engine, it has been proposed to provide individual spark coils each mounted to the tip of a respective spark plug for firing the spark plug. Such ignition systems provide higher ignition power and better performance. However, in conjunction with such ignition systems there arise certain problems in connection with the spacial disposition of all of the components of the engine.
This problem is particularly acute in conjunction with engine having multiple valves mounted in an overhead fashion. Although it is easy to avoid interference with the valves by placing the spark coils higher in the cylinder head, this adversely affects the overall height of the engine. Therefore, it is desirable to provide a low mounting for the ignition coil. However, this gives rise to certain difficulties, particularly when the valve actuating mechanism for a multiple valve engine is considered.
Although it is possible to lower the ignition coil by canting the axes of reciprocation of the valves in an outboard fashion, this has adverse effects. That is, as the angle of reciprocation of the valves is increased, the heads of the valves define a more steeply inclined combustion chamber and one which has a large surface area and large combustion chamber volume. Both results are to be avoided. Large surface areas provide large quench areas that can reduce the performance of the engine. Large combustion chamber volumes also dictate a low compression ratio which itself deteriorates from the engine performance.
It is, therefore, a principal object to this invention to provide an improved ignition system for a multi-valve engine which permits the use of a spark coil mounted on the spark plug and yet permits a compact engine configuration.
It is a further object to this invention to provide an improved ignition system for an engine having a spark plug mounted spark coil wherein a compact engine can be provided, multi-valves employed and a high compression ratio and compact combustion chamber surface will result.